Data protection and emails

Can a charity (PTA) which has a list of email contacts use their email list to distribute information about a campaigning that is not to do with fundraising? As far as I am aware they have no data protection policy.

If names and addresses are collected by an organisation to be used by that organisation then they are bound by The Data Protection Act and info must not be shared with a third party without the individuals permission. If the individual leaves the organisation then their info should be removed.Using the list for sharing info not linked to the organisation is therefore shouldn't be done nor is it good practice.

If the campaigning group has not been given the list there has not been a data breach. It could possibly be argued that the PTA has used the email addresses for a purpose other than that for which they were obtained. They ought to have a system in place whereby contacts can opt out from receiving such communications.